armature reactance is affected by the rotating field of the stator. As the reactance formula contains a frequency quantity, the armature reactance changes in relationship to the difference in frequency between the armature and stator fields.

I think what you are referring to is called the "armature reaction," or back EMF, which is a phenomenon caused by flux coupling to the armature from the field. The armature reactance is the complex portion of the impedance of the armature winding due to its leakage inductance.